Roofing and the like



Patented July 15, 1941 h 2,240,698 l v V v nooF'ING AND THi Lmr Richard A. Wilkins, Rome, Ni irassignor to Revere- Copper and Brass Incorporated, Rome, I

N. Y., a corporation of Maryland 7 No' Drawing, Application March 28, 1941, 7 Serial'No. 385,681

My invention relates to roofing and the like, and particularly to improvements in the roofing forming the subject matter of mypending'applL cations Serial Number 363,515, filed October 30,

1940, and Serial Numbers 381,697 and 381,698, both filed-March 4, 1941. V 4

As pointed out in the above mentioned pending applications, the material heretofore commonly employed for copper roofing, sheathing, and other exposed protective coverings for buildings hasv been thin rolled sheets of'highly refined copper. Further, in refining copper for thesepurposes it has heretofore always been the practice of producers thereof to remove so vfar as possible all impurities so as to secure as pure 'a copper as possible. The known high resistance of, pure copper generally to chemical corrosion, and the observed fact that impurities commonly foundin rolled copper tend to make it less ductile in both the hot and cold rolled conditions, more difficult to produce by either hot or cold rolling, and commonly "cold short in the sense that it tends to crackwhen bent or otherwise cold worked, have caused pure copper heretofore to.be considered the most satisfactory commercially available ma-.

terial for light weight metal roofingrandnthelike. In fact during the past forty years copper roofing has for these reasons been made almostexclus'ive of electrolytically refined copper, which commonly is 99.9% pure copper.

Nevertheless it is a frequently observed fact that copper roofing, even whennsubstantiallyj 100% pure electrolytically refined copper, often fails in use, being subject to cracking sufiicientfto' render it non-waterproof. Heretofore it'was 'be lieved that these cracks were caused by mechanical fatigue resulting'by reason of the cyclic stresses set up by alternate expansion and con traction of the copper sheets under varying. temperature conditions. For that reason builders heretofore have resorted to expensive roof constr'uctions, and various expensive expedients such I as corrugating the roofing. and the employment of elaborately designed expansion joints, andthe:

use of heavy gauge copper in the attempt to relieve or reduce the effect on the roofing of these cyclic stresses and thereby eliminate so far as possible this form of failure. Although these attempts have been partially successful, the exr pense incidental thereto, andthe many failures which actually have occurred in spiteof these precautions, have seriously interfered with the general adoption of this otherwise very satisfactory roofing.

As pointed out in app'licants pending applicaof the material is exceeded, and as tions above referred to, applicant has found that the jfailureof copper roofing and the like heretofore has notbeen correctly understood. This material, he has found, does not fail primarily b'y reason-or the-cyclic stresses to which it is -subje'cted when in use, as heretofore believed, but,

strangely enough, primarily by reason of a heretofore wholly unsuspected type of corrosion which occurs'when thishig'hly pure copper is exposed to'an atmosphere contaminated'by wind borne products of combustion of 'modern domestic and industrial fuel "burning appliances and industrial atmospheres" in general. I

Applicant has found, that upon removing the 1 patina and "other accumulated corrosion products from copper'roofing whichhas failed, the copper roofing *sur face'thus exposed is characteristically pitted, instead ;of 1 being its" smooth unpitted conditionfin which it originally left the rolling mill or the'metal showing a uniform'decrease in thickness over-its whole surface due to corrosion;

His "investigations show that these pits are caused by the'iormation on the copper, when ekp'osed to a contaminated atmosphere, of a film oi corrosion products which is characterized by a lack of adhesion to't'he copper, a lack of tenacity in re'sp'c't'to 'failure, and a tendency toward 'pervi- I ousness' which allow the copper to be attacked locally rather than uniformly by the corrosive media and'thereb'y result in the formation of sharply definedfinwa-rdly pointed pits in the'nature ofnotch'es; He has found that copper so attacked rapidly fails when subjected to the'cyclic' stresseshereinbefore referred to by reason o'fth'e' natural tendency of the stresses to be concen-' trated inthe metal below the bottoms of the notch-"like pits. As a'result of this concentration of the stresses, the: metal below the bottoms of the pits 'workhardens and the fatigue strength a result the metalscracks, at the pits.

Pure copper roofing applicant has found is comparatively sensitive to this notch effect, when causedby a combination of chemical corrosion and subjection to cyclic stresses,"on account of the film which forms on it causing the pure cop.-

per to pit-and the great sensitivity of pure copper to work-hardening when cold worked.

The above mentioned applications point out that this type of failure of copper roofing'ascon structed from thin-sheets, commonly from 0.003

to 0.03 inch in thickness, can be substantially entir'ely avoided by incorporating into the copper controlled amounts of arsenic or antimony, or both.

worked, and therefore any scratches, d t or e v phosphorus.

- and to failure by reason of notch effect is also inlike in the nature of notches whichmight be formed during the handling or installation of the roofing will not cause it to fail by reason of notch defect. In other words, the action of these substances on the roofing is twofold: it prevents notches from being formed by corrosion and pre-.i

vents the roofing failing by notch effect even if the notches are accidentally formed b mechanical means.

It has-been found that the presence. of the proper amounts of arsenic or antimony, or both, in the copper-roofing produces-on the roofing surface a corrosion film which is tenacious,'a'dherent, impervious and non-hygroscopic, the filmbeing comparably as ductile as the copper base material itself, thus permitting the roofing to be repeatedly bent without ruptur of the film or interruption of its adherence to thecopper. Thus this film effectively protects the underlying base material. from contaminated air and moisture, and in this way effectively eliminates the possibility of the formation of the above mentioned notch-like pits, for any slight amount of corrosion which occurs will be uniformly distributed over the surface of the. copper. importantly this film has the property of being self-healingin thesense that if, for ,any:reason its continuity is locally interrupted it will rapidlyreform when subjected to corrosion and thus act to prevent substantial local corrosion at the, interrupted regions which in apure copper would continue to corrode at any accelerated rate re-, sulting in pitting at the point of interruption of the-film. a H 1 Applicant has now found-that phosphorus may be substituted for arsenic or antimony, or a com-- roofing surface, when subjecteclto atmospheric corrosion, nan instantly self-healing, tenacious, adherent, impervious, non-hygroscopic film, ap-

parently formed ofa phosphorus content com-' pound, while rendering the copper roofing less sensitive to failure by reason of .notch effect than sheet copper without the phosphorus when subjected to the cyclic stresses caused by .expansion and contraction of the roofing. The film which forms when phosphorus is present, however, is thicker, and self-heals more quickly, than the films caused by the presence of arsenic or antimony, or both. Further, phosphorus, it has been found,'has the most important effect of very markedly reducing the heat conductivity of the copper roofing, this reduction in heat conductivity being as low as 50% of that of pure copper in some instances within the range that will produce the other desirable effects. Because phos-'- phorus produces this improved film and increases the insulating effect of the roofing, and. further because the film is of a pleasing brownish black appearanca'makes the roofing solder more easily, and increases the tensile'and fatigue strengths of the copper'roofing and'in general its ductility,

Most

2,249,698 r '1; if

its use, it has been found, is very desirable in this connection.

It has been found that within the ranges of 0.1 to 1% phosphorus the copper has a greater tensile strength and is more ductile when cold than pure copper, the tensile strength increasing with the amount of phosphorus, Bhosphorus within this range also increases :the fatigue strength of the copp'enroofin'g, the fatigue strength being at a maximum at about 0.4 to 0.5% The resistance to work hardening creased by additions of phosphorus within the range'of 0.1 to 1%, being at a maximum at about 0.4 to 0.6%. Throughout the range of 0.1 to 1% phosphorus the tenacious, self-healing, adherent,

protective film forms, and the copper can be comtend .to make the copper roofingv containing phosphorus approach the poor resistance of pure coppiergroofing to corrosion and its sensitivity to notch effect, and thereby act to destroy the beneficial efiects of the phosphorus. The pres-,

ence of. 'such substances as cobalt,jtin, silicon and zinc insubstantial amounts had also best .be avoided asthey tend to increase the sensitivity, of the copper roofing to work hardening and. notch effect; Thus it .will be ,understood,. that in the sense the copper roofing does notcontain deleterious substances or. amounts thereof which substantially destroy the beneficial effects tended to beimpartedby the phosphoru s thebalance. of the alloy aside from the phosphorus is'essentially copper.

, In making the roofing according to theiinv en tion the copper may be melted, and the phos.

phorus added to the melt in the formof phosphor-copper. The molten metal may then be cast into slabs, whichlatter may be rolled into sheets of desired thickness .by the usual mill process of rolling copper roofingsheets. v Finally the rolled sheets may be annealed to the". degree cyclic stresses of softness that will best resist the towhich they are subiectedwhen in use.

For'convenience in terminology the article ofv manufacture according to the invention is termed roofing, it being understood that'as used in. the a pended ,claims'such term includes various shingles, sheathings, valleys, and like-protective coverings for buildings, as well as what in a more limited sense is ordinarily termed roofing. Also it will be understood that the roofing according to the invention, comprises sheet copper presenting an extensive external roofing surface,

and may in this sense consist of a backing having an exterior sheet of copper as well as consist wholly of sheet copper.

I claim:

1; Roofing. comprising sheet copper presenting an extensiveexternal roofing surface, the copper being alloyedwith such amount of phosphorus between 0.1 and 1% as will cause the formation on said surface when exposed to atmospheric corrosion of a self-healing, adherent, protective film composed predominantly of phosphorus content compound, while rendering the sheet copper less sensitive to failure by reason of notch efiect than sheet copper without the phosphorus when subjected to the cyclic stresses caused by expansion and contraction of the roofing.

2. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with approximately 0.1 to 1% phosphorus, the balance of the alloy in respect to the phosphorus .being essentially copper.

3. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with approximately 0.4 to 0.6% phosphorus, the balance of the alloy in respect to the phosphorus being essentially copper.

RICHARD A. WILKINS.

CERTIFICATE OF CORRECTION. Patent No. 2,219,698. July 1 19L 1. I

' RICHARD A. WILKINS. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column,- line 15, for the word "defect" read "effect"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office; Signed and sealed this 16th day of September, A. D. 191d.

Henry Van Arsdale,

(seal) Acting Commissioner of Patents. 

